In recent years, a phase change memory (PCM) has been developed as one type of a semiconductor memory device. In a PCM device, a crystallinity state (material phase) of a variable resistant element is changed by application of a voltage. By change of phase, the variable resistant element can be switched between a low resistance state (LRS) or a high resistance state (HRS). Data can be stored in a phase change memory cell by the setting of one the two states to correspond to binary data values or the like.